A new health study shows that although East Boston was hit hard by the first wave of the 2009 H1N1 influenza (swine flu) last spring, the disease has virtually disappeared here — but public health officials are still weary of another outbreak.
As spring turned to autumn in East Boston, the 2009 H1N1 influenza virus moved from children and teens to older age groups. The flu then virtually disappeared from some neighborhoods like Eastie but hung around in others, and continued to disproportionately impact communities of color like Dorchester, Roxbury and Mattapan, according to the study released by the Boston Public Health Commission.
The study, titled “The State of the 2009 H1N1 Pandemic: Boston,” was released as National Influenza Vaccination Week kicked off from January 10-16. The report revealed the unpredictable twists and turns of the virus as it swept through Boston neighborhoods from last April through December, raising the prospect that a third wave of H1N1 flu could strike the city at anytime.
“This study is proof positive that we can ill-afford to let down our guards,” said Dr. Barbara Ferrer, executive director of the Boston Public Health Commission. “Now more than ever people should be vigilant and get vaccinated, which is the best protection against the 2009 H1N1 virus.”
Estimating illness by neighborhood, the report found high amounts of flulike illness in Eastie in the spring and much less in autumn while there were more illness in the Fenway and Back Bay neighborhoods in autumn than in spring and high amounts of illness in North Dorchester in both spring and autumn.
More disturbingly, racial disparities persisted throughout spring and autumn, with black and Hispanic residents more often hospitalized. Of hospitalized flu cases, 37.5 percent were black and 29.7 percent were Hispanic, compared to 24.1 percent of whites.
The study, based on data collected and analyzed by the Commission’s Infectious Disease Bureau, found that people between ages five and 17 accounted for 44 percent of confirmed H1N1 and non-specified influenza cases in the spring, or between April 16 and July 25, 2009. But by the time the virus’s second wave hit, the picture had changed and people between ages 18 and 44 accounted for 44 percent of reported cases between August 30 and December 12.
The same held true for hospitalizations: 26 percent of the people hospitalized in the spring were ages five through 17 and in autumn 31 percent were between 18 and 44.
“It’s a typical pattern for flu – it starts with young, school-age children, then spreads to their moms and dads, and eventually gets into the older adult population,’’ said study author Julia Gunn, director of the Communicable Diseases Division in the Infectious Disease Bureau.
Dr. Ferrer said the data will be used to inform the Public Health Commission’s education and outreach efforts and media campaign, which are swinging into high gear for National Influenza Vaccination Week.
“We’ve likely not seen the end of the 2009 H1N1 outbreak and the public needs to know that and get vaccinated,’’ she said. “We will keep repeating that message until flu season ends or there’s no more flu in Boston.”
For a copy of the full report, visit www. bphc.org; to find a free flu clinic call 617-534-5050.